Tubular element made of carbon fiber-based composite material

ABSTRACT

A tubular element made of composite material, comprising a plurality of layers of structural fibers, which are superimposed and arranged so that the fibers lie along preset directions and are immersed in a matrix of the polymeric type. A predefined amount of at least one color is provided in the polymeric matrix of the outermost layer, substantially only proximate to the outermost surface thereof.

The present invention relates to a tubular element made of carbonfiber-based composite material.

BACKGROUND OF THE INVENTION

In many fields, particularly in the sports field, it is necessary toresort to tubular elements made of carbon fiber-based composite material(as a consequence of its excellent mechanical characteristics combinedwith low weight) to manufacture equipment: consider for example fishingrods, but also the masts of windsurfs (or of sailing boats), golf clubsor ski poles.

All these elements need, for various reasons, to have an externalsurface that is colored (or bears designs or lettering): however, thiscoloring must not reduce in any way the mechanical properties and mustbe resistant enough to avoid being abraded during the stresses to whichthe sports implement is subjected during use.

In particular, fishing rods for the Roubaisienne technique made ofcarbon fiber are currently the type of fishing rod that has the bestmechanical characteristics (by combining an optimum dynamic elasticaction with extremely low weight and good resistance to externalagents).

The fishing technique that uses fishing rods of the Roubaisienne typerequires the segments of the rod, during fishing, to be continuouslyassembled and disassembled (by mutual insertion) in order to change thelength of the rod, making it in each instance suitable for the actionbeing performed.

During fishing, these carbon-fiber fishing rods are subjected to theincidence of solar radiation: after long periods under the sun, theirexternal surface is overheated considerably, and this can causeunpleasant sensations in the angler who has to handle it.

In order to reduce the heating caused by solar irradiation, it would beconvenient to provide carbon fiber rods in which the surface is notblack and better still non-reflective.

External painting of the rod elements is a scarcely interestingsolution, owing to the fact that the deposited layer of paint can alterthe elastic response and the thickness of the rod. When using a rod witha painted external surface, it is noted that in a short time thesurfaces along which one acts most frequently with one's hands losetheir coloring, in practice eliminating the advantages obtained withsaid coloring.

In order to ensure good resistance of the paint, one might considerabrading slightly the surface of the rod element (before painting) inorder to ensure better bonding of the color: this choice necessarilyentails damaging the outermost carbon fibers, consequently degrading themechanical properties of the element being treated.

The application of colored adhesive films is also to be consideredextremely negative, since it greatly modifies the elastic responsecharacteristics of the rod element due to the increase in weight that itentails.

In any case, the colored layers modify substantially the externalsurface of the rod element, generally reducing its slidability.

In fishing with Roubaisienne rods, slidability in the hands of theangler is fundamental, indeed because the fishing action is based on themodularity of the rod, which can be extended or shortened by insertingor removing rod elements. To perform these operations on the rod, it istherefore necessary to slide it in the palm of one's hand: theseoperations are often performed while a load is applied (a fish hangingfrom the line or also the weight of the rod itself) and it becomesfundamental for the slidability to be as high as possible.

Excessive heating of the surface by irradiation is a problem also infishing with telescopic rods, which are provided with a reel.

On the other hand, coloring obtained with conventional methods is notadvisable, since it alters the slidability of the line dispensed by thereel on the external surface and causes penalization during casting.When the angler casts the bait towards the intended position, the linein fact unwinds rapidly from the reel and travels rapidly, skimming theexternal surface of the various rod elements: the lower the friction ofthe line on the external surface, the greater the distance reached bythe bait with the casting action.

Owing to the need to allow to distinguish immediately different segmentsof the Roubaisienne rod, thus facilitating the organization of thefishing session, and in order to give distinctive characteristics todifferent telescopic rods (which belong for example to a same series andtherefore can be confused easily), it is necessary to provide smallportions that are colored differently (and ideally also bear designs,lettering or initial). Currently, this is possible only by painting orscreen printing or by applying adhesive laminas.

The need to customize the external surface of the tubular elements oreven just give them different colorings so as to allow to distinguishimmediately elements that are similar but have different characteristicsis also felt in many other fields of sport (for example, for the mastsin sailing sports, for golf clubs, for tennis rackets, for ski poles,etc.).

SUMMARY OF THE INVENTION

The aim of the present invention is to obviate the cited drawbacks andmeet the mentioned requirements, by providing a tubular element made ofpigmented composite material that does not have variations in weight,thickness and roughness in the transition from a pigmented region to anon-pigmented region.

Positively, an object of the present invention is to provide a tubularelement that has distinctive surface colorings that preserve itsmechanical properties.

Advantageously, another object of the present invention is to provide atubular element that has high surface slidability.

Within this aim and these objects, another object of the presentinvention is to provide a tubular element that is simple, relativelyeasy to provide in practice, safe in use, effective in operation, andhas a relatively low cost.

This aim and these and other objects that will become better apparenthereinafter are achieved by the present tubular element made ofcomposite material, of the type that comprises a plurality of layers ofstructural fibers, which are superimposed and arranged so that thefibers lie along preset directions, said fibers being immersed in amatrix of the polymeric type, characterized in that a predefined amountof at least one color is provided in the polymeric matrix of theoutermost layer, substantially only proximate to the outermost surfacethereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention willbecome better apparent from the following detailed description of apreferred but not exclusive embodiment of a tubular element made ofcarbon fiber, illustrated by way of non-limiting example in theaccompanying drawings, wherein:

FIG. 1 is a schematic perspective view of a plurality of layers ofstructural fibers immersed in a polymeric matrix and superimposed;

FIG. 2 is a schematic perspective view of the arrangement of the layerson a rigid core;

FIG. 3 is a schematic perspective view of the deposition of a film ofcolor on the surface of a tape made of a material such as plastics;

FIG. 4 is a schematic perspective view of the wrapping of a pigmentedtape, according to a first method with a pitch that correspondsapproximately to the width of said tape with partial overlap, on thelayers of fibers arranged on the rigid core;

FIG. 5 is a schematic perspective view of the wrapping of a pigmentedtape, according to a second method with an infinite pitch, on the layersof fibers arranged on the rigid core;

FIG. 6 is a schematic perspective view of the wrapping, over saidpigmented tape, of a second pressing tape with a tight pitch;

FIG. 7 is a schematic perspective view of the heating of the element onwhich the two tapes are wrapped;

FIG. 8 is a schematic perspective view of a tubular element according tothe invention;

FIG. 9 is a schematic perspective view of a tubular element according tothe invention;

FIG. 10 is an enlarged-scale sectional view of a portion of a tubularelement around which a pigmented tape is wrapped;

FIG. 11 is an enlarged-scale sectional view of a portion of a tubularelement around which a pigmented tape is wrapped, during thermoforming;

FIG. 12 is an enlarged-scale sectional view of a portion of a tubularelement according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the figures, a tubular element made of compositematerial according to the invention is generally designated by thereference numeral 1.

The description that follows describes an element 1 for fishing rods;this description is non-limiting to the only embodiment that isdescribed, since the characteristics that are given and themanufacturing method used are the same for all the types of element 1that can be provided, be they components of fishing rods, of masts forsailing sports, of tennis rackets, ski poles, or others.

Each element 1 of the fishing rod is constituted by a plurality oflayers 2 (2 a, 2 b and 2 c) made of composite material (structuralfibers and polymeric matrix), which are superimposed and are arranged sothat their fibers lie along presets directions, in order to optimize themechanical characteristics of the layer 2 in those directions.

In each one of these layers 2, the fibers (generally carbon fibers, butas an alternative it is also possible to use glass fibers or othermaterials) are embedded in a matrix of the polymeric type; such matrixis generally constituted by a thermosetting resin (for example epoxyresin), which is polymerized in the final step of production of thetubular element 1, which is known as thermoforming.

In a particularly effective embodiment, the outermost layer 2 a of anelement 1 provided according to the invention has, on its outer surface,a uniformly distributed infinitesimal surface roughness 3.

The presence of this infinitesimal roughness 3, combined with thesurface hardness of the element 1 caused by the mechanicalcharacteristics of the resin that impregnates the layers 2, facilitatesthe sliding of the hands of the angler on the surface: microscopicamounts of humidity may remain trapped in the successive continuoushollows of the surface, providing substantially a sort of lubrication.

With respect to the smooth surface of conventional fishing rods, thereis a considerable improvement of the fishing action, caused by theimmediate slidability, with a considerable reduction of the abrasion ofthe palm of the hand of the user in case of prolonged use.

As already mentioned, the described solution relates to elements 1 of afishing rod, but actually surface slidability is advantageous in manysituations that recur also in other sports: consider for example the bagof a sail that must be able to slide easily on the mast of a windsurf,for example.

In other embodiments, the surface of the element 1 can also becompletely smooth (polished) or have any degree of surface roughnesscomprised between the two extreme cases of a smooth (polished) surfaceand of a surface with infinitesimal roughness 3 (intrinsic opacity).

The polymeric matrix of the outermost layer 2 a contains a predefinedquantity of at least one color: the pigmented resin 4 (part of thematrix of layer 2 a within which the color is present) ensuresreflection of part of the solar radiation that strikes the fishing rodelement 1, keeping its temperature at lower values than conventionalfishing rods.

Conventional fishing rods made of a composite based on carbon fiber areexternally black and polished: because of these surface characteristics,they can reach high temperatures (which as such are unpleasant orpainful upon contact with the hands, as already mentioned followingcontinuous assembly and disassembly of the component segments) due tosolar irradiation.

The color is not distributed on the outer surface of the layer 2 a: theelementary color particles 5 that are present in the pigmented resin 4are in the layer 2 a, since they are diffused in the polymeric matrix inthe region that faces the external surface.

In practice, the particles 5 are embedded in the polymeric resin, whichconstitutes the matrix of the composite of the layer 2 a at itsoutermost region, giving a particular coloring to the element 1 from anintrinsic standpoint (one of the components of the layer 2 a, thepolymeric resin, in fact assumes the coloring determined by the presenceof the color particles 5).

The surface of the layer 2 a does not undergo any change in roughness 3as a consequence of the presence of the particles of color 5.

The external surface of the layer 2 a generally has a ridge 3 a, whichis arranged in a spiral along the element 1 and has a reduced height; incertain cases, the ridge 3 a can also be substantially imperceptible oreven omitted.

The structural fibers 6 (carbon fibers) of the layer 2 a aresubstantially intact and have no internal tensions caused by thepresence of particles of color 5 in the pigmented resin 4 interposedbetween individual fibers 6: this is because the penetration of theparticles of color 5 does not affect, or occurs all through the entirelayer 2 a but affects only the outermost region (without thereforeaffecting the structural fibers 6) and because the particles 5 areembedded uniformly in the polymeric resin that constitutes the matrix.

The particles of color 5 are provided inside the matrix of the polymerictype (they are embedded in it) in a variable quantity and are uniformlydistributed: this ensures that the appearance of the fishing rod element1 is uniform in terms of color distribution, ensuring that even if theamount of color particles 5 is small, it is not possible to identifyregions that are more (or less) colored.

Optionally, the particles of color 5 can be distributed only on someportions of the rod element 1: in this manner, it is possible to provideon the surface of the rod element 1 shapes and particular colorcombinations, according for example to a distinctive symbol or mark. Theadvantage of this embodiment is that the mark thus impressed is notsubjected to abrasion, since the color is mixed, in the external regionof the layer 2 a, with the polymeric matrix of the layer 2 a.

Another possibility is to provide the pigmented resin 4 with a mixtureof elementary pigments 5 of different colors, obtaining any type ofcolor or design on the surface of the rod element 1.

This refinement is obviously of great interest for all sectors in whichtubular elements 1 are used. In particular in the sports field, it isextremely useful to be able to give particular colorings or imprintmarkings or distinctive designs on the surface of the equipment in orderto facilitate its use and improve its appearance.

The particles of color 5 and the polymeric matrix have a glasstransition temperature on the same order of magnitude: in this manner,during thermoforming the particles of color 5 can diffuse inside thematrix (which in this step undergoes an initial softening) withoutrisking that one of the two materials hardens before the other or, worsestill, degrades as a consequence of an excessively high temperature.

In order to obtain the tubular element 1, it is necessary to superimposeat least two layers of structural fibers 2 impregnated with polymericresin, shaping them substantially like a tubular body by wrapping arounda rigid core 8 (which is generally metallic).

It is necessary to deposit beforehand, with the intended distribution,at least one type of particle of color 5 on a tape 9: the tape 9 can becompletely smooth (shiny) on both of its flat surfaces or can beprovided with at least one surface that has at an infinitesimal surfaceroughness 3.

If the surface with infinitesimal surface roughness 3 is provided, thedeposition is to be provided on said surface.

The color particles 5 must be deposited according to traditionalprocesses, such as a rotogravure or actual painting (or alsoflexography, screen printing, or any other method suitable for thepurpose), within a suitable apparatus 11.

At this point, it is necessary to wrap the pigmented tape 10 over thelayers 2 of structural fibers wrapped around the core 8, keeping it withthe pigmented surface in contact with the outermost layer of fibers, andwith a substantially helical path.

If one wishes to wrap the tape 10 with an infinite (or nil) pitch, thetape 10 is arranged longitudinally with respect to the element 1 (ortransversely, if the tape 10 is arranged with a nil pitch and istherefore as wide as the element 1 is long).

A second wrapping, which this time is tighter and more forced, above thewrapped pigmented tape 10 must be performed with an additional pressingtape 12, again with a helical arrangement but this time with a tightpitch.

After performing the second wrapping, the core 8, the layers of fibers 2and the wrapped tapes 10 and 12 must be arranged in a high-temperatureenvironment in order to facilitate the diffusion of the color particles5 within the polymeric matrix of the outermost layer 2 a, in order toimpart the infinitesimal surface roughness 3 of the pigmented tape 10(therefore, if a tape with these surface characteristics has beenchosen) on the outer surface of the outermost layer 2 a and in order tofacilitate the cross-linking of the polymer that constitutes thethermoforming matrix.

The tape provided with at least one surface having infinitesimal surfaceroughness 3 is made of a material of the thermoplastic type, suitablefor the temporary adhesion of the color particles 5 but not forpermanent adhesion (thus facilitating the separation of said particlesduring thermoforming and their migration toward the inside of the matrixof the layer 2 a).

After the thermoforming step, the tubular element 1 is extracted fromthe core 8 and the tapes 10 and 12 are removed from the surface of theelement 1, which therefore retains the coloring due to the diffusion ofthe color particles 5 (released by the tape 10) inside the layer 2 a,and the infinitesimal surface roughness 3 imparted by the tape 10.

The operation of the invention is intuitive: by using a fishing rodconstituted by elements 1 according to the invention, the angler isfacilitated in his action owing to the high surface slidability causedby the presence of the infinitesimal roughness 3 of its surface. Asmentioned, trapping particles of water in the minute cavities andrecesses of the surface of the element 1 ensures maximum slidabilitythereof in the palm of the hand of the angler. This slidability can beidentified immediately even in fishing rods of the telescopic type sincethe line, released by the reel, during launching glides on the surfacewith maximum slidability. It should be noted that the infinitesimalroughness 3 decreases the aerodynamic drag of the fishing rod duringcasting. Likewise, the bag of the sail of a windsurf slides easily alongthe shaft, facilitating its assembly.

The surface further has a particular coloring caused by the diffusion ofthe color inside the polymeric matrix: in this manner, the tubularelement 1 can be provided in any color (according to the technicalrequirements of the user but also according to commercial requirements).

Advantageously, said coloring does not abrade with use and it is notpossible to detect an increase in thickness at the regions where thecolor is applied.

Conveniently, the addition of weight is undetectable, since the color isembedded within the polymeric matrix and therefore the amount of colorrequired to give the intended color is very low.

Conveniently, the method for obtaining the element 1 is far lesspollutant than conventional solutions for surface coloring, since theamount of color needed to give the chosen color is low and also thedispersion of color is minimum, since the deposition of the color isperformed on a tape (not directly on the surface of the element 1)according to highly efficient methods, which also require (with respectto conventional painting) the use of lower amounts of solvents.

Positively, the color is distributed uniformly along the rod element 1(according to the requirements of the manufacturer) without producinginternal tensions between contiguous fibers caused by the interpositionof particles 5.

The provision of tubular elements 1 according to the invention furtherallows to imprint flight designs (even logos or lettering) to theelement 1 according to the described method. Although these imprintingsdo not modify the mechanical and structural characteristics of the rodelement 1, they can give it a distinctiveness with respect to othersimilar products, ensuring differentiation of production.

It has thus been shown that the invention achieves the intended aim andobjects.

The invention thus conceived is susceptible of numerous modificationsand variations, all of which are within the scope of the appendedclaims.

All the details may further be replaced with other technicallyequivalent ones.

In the embodiments that follow, individual characteristics, given inrelation to specific examples, may actually be interchanged with otherdifferent characteristics that exist in other embodiments.

Moreover, it is noted that anything found to be already known during thepatenting process is understood not to be claimed and to be the subjectof a disclaimer.

In practice, the materials used, as well as the shapes and dimensions,may be any according to requirements without thereby abandoning thescope of the protection of the appended claims.

The disclosures in Italian Patent Application No. BO2004A000474 fromwhich this application claims priority are incorporated herein byreference.

1. A tubular element made of a composite material, comprising: aplurality of layers of structural fibers, said layers being superimposedand arranged so that the structural fibers lie along preset directions;a matrix of a polymeric type, in which said structural fibers areimmersed; and a predefined amount of at least one color provided in thepolymeric matrix of an outermost one of said plurality of layers, saidamount of at least one color being provided substantially only betweenan outermost surface of the outermost layer and a region thereof wheresaid structural fibers are arranged.
 2. The tubular element of claim 1,wherein said outer surface has at least one ridge, which is arrangedalong the tubular element and has a height of less than 120 micrometers.3. The tubular element of claim 1, wherein said outermost layer has anouter surface with an infinitesimal and uniformly distributed surfaceroughness which is intrinsic to said matrix, said outer surface havingan opaque appearance.
 4. The tubular element of claim 1, wherein saidamount of at least one color is provided in particle form, withparticles of color that are present in the polymeric matrix in theoutermost layer of fibers, said particles having a regular spatialdistribution according to all longitudinal, radial and angularcoordinates.
 5. The tubular element of claim 1, wherein said outermostlayer is free of internal tensions and degradations caused by a presenceof said predefined amount of at least one color.
 6. The tubular elementof claim 1, wherein said predefined amount of at least one color isprovided distributed uniformly over an entire surface of the tubularelement.
 7. The tubular element of claim 1, wherein said predefinedamount of at least one color is provided distributed only on somesurface portions of the tubular element.
 8. The tubular element of claim1, wherein said predefined amount of at least one color is provideddistributed according to a shape and color of at least one distinctivemarking.
 9. The tubular element of claim 1, wherein said predefinedamount of at least one color is constituted by a mixture of elementarypigments of different colors.
 10. The tubular element of claim 1,wherein said predefined amount of at least one color and said polymericmatrix have a glass transition temperature on a same order of magnitude.11. The tubular element of claim 1, wherein said predefined amount of atleast one color is provided divided among a plurality of spotsdistributed on the surface of the tubular element.
 12. A method forproviding a tubular element made of composite material, comprising thesteps of: superimposing at least two layers of structural fibersimpregnated with a polymeric matrix, and shaping said layerssubstantially like a tube by wrapping around a rigid core; depositing,with an intended distribution, a predefined amount of at least one coloron at least one surface of a first tape, providing a pigmented tape;wrapping said pigmented tape around said layers wrapped around saidcore, with a pigmented surface in contact with an outermost one of saidlayers; wrapping, by tightening and forcing, on said layers wound aroundsaid core, above said pigmented layer, a second pressing tape, which hasa tight helical pitch in order to compress said layers and the pigmentedtape on said core; and placing the core, said layers and the wrappedtapes in a high-temperature environment in order to facilitate diffusionof color inside the polymeric matrix of the outermost layer andsimultaneously facilitate cross-linking of the polymer that constitutessaid matrix for thermoforming.
 13. The method of claim 12, wherein saidfirst tape is provided with at least one surface that has aninfinitesimal surface roughness with an opaque appearance, withdeposition of said color being provided on the surface that has saidroughness.
 14. The method of claim 12, comprising after thethermoforming step removal from the tubular element of said secondpressing tape and said pigmented tape and extraction of the core fromthe tubular element.
 15. The method of claim 12, wherein wrapping ofsaid pigmented layer is carried out with a substantially helicalorientation with an optionally infinite pitch.
 16. The method of claim12, wherein wrapping of said pigmented tape is carried out with asubstantially helical orientation and with an optionally nil pitch. 17.The method of claim 12, wherein said first tape is provided with atleast one surface that has an infinitesimal surface roughness and anopaque appearance which is made of a thermoplastic resin, which issuitable for temporary adhesion but not for permanent adhesion of thecolor.